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There are years of drought in a small, relatively isolated community. During the drought, small seeds with thin shells become rare. Large seeds with hard cases become increasingly common. The large, tough seeds are successfully eaten by birds with large and broad beaks. Assuming that the drought continues and the population of birds in the community stays isolated, what predictions for the population can you make under the influence of natural selection? a. The birds with small, thin beaks will grow larger, broader beaks to be able to eat the larger seeds. This will result in subsequent generations having a higher percentage of birds with large, broad beaks. b. There will be more birds with small, thin beaks dying and more birds with large, broad beaks surviving. Differential reproduction of birds with large, broad beaks will result in subsequent generations having a higher percentage of birds with large, broad beaks. c. The species will diverge into two species, one with small, thin beaks and one with large, broad beaks. The two species will then compete for resources. d. There will be neither phenotypic nor genotypic changes in the population.

Step by step solution

01

Understand Natural Selection

Natural selection is a process where individuals with certain heritable traits tend to survive and reproduce more successfully than others because those traits are better suited to the environment.

02

Identify the Environmental Pressure

In this scenario, the environmental pressure is the drought, which has caused smaller seeds with thin shells to become rare and larger seeds with hard cases to become common.

03

Identify the Traits That Confer an Advantage

Birds with large, broad beaks are able to eat the larger seeds, which gives them a survival advantage compared to birds with small, thin beaks.

04

Analyze the Impact on Bird Population

Birds with large, broad beaks are more likely to survive and reproduce. These birds will pass on their traits to their offspring, resulting in subsequent generations having a higher percentage of birds with large, broad beaks.

05

Eliminate Incorrect Options

Option (a) suggests that birds with small, thin beaks will grow large, broad beaks in their lifetime, which is incorrect as acquired traits are not inherited. Option (c) suggests species divergence, which usually takes a long time and more than just food availability changes. Option (d) states there will be no changes, disregarding natural selection.

06

Select the Correct Prediction

Option (b) correctly describes natural selection. There will be more birds with small, thin beaks dying and more birds with large, broad beaks surviving. This will result in a higher percentage of birds with large, broad beaks in subsequent generations.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

evolutionary biology

Evolutionary biology is the study of how organisms change over time through processes like natural selection and genetic drift. This field aims to understand the origins and adaptations of species. Organisms evolve to become better adapted to their environments. This can involve changes in physical traits, behaviors, or even metabolic processes. Evolutionary biology combines genetics, paleontology, and ecology to give us a full picture of life's history. For instance, the drought scenario in the bird community is a classic study subject in evolutionary biology because it shows how environmental pressures can shape physical traits over generations.

adaptive traits

Adaptive traits are characteristics that improve an organism's ability to survive and reproduce in its environment. These traits can be physical, like the large, broad beaks in birds, or behavioral, like specific feeding habits. In the bird population affected by drought, large and broad beaks are considered adaptive traits. These beaks help birds break open the tough seeds that have become common, allowing them to obtain food more easily. Over time, adaptive traits become more common in a population because individuals with these traits are more likely to survive and reproduce. It's important to note that these traits are heritable, meaning they can be passed down to offspring.

survival of the fittest

Survival of the fittest is a concept introduced by Charles Darwin to describe the mechanism of natural selection. It refers to the idea that individuals best adapted to their environment are more likely to survive and reproduce. In the bird scenario, birds with large, broad beaks are the 'fittest' because they can access the available food sources. The birds with small, thin beaks are less likely to survive the drought because they can't eat the larger seeds. Thus, 'fittest' doesn't mean the strongest or the fastest, but the best suited to the current environment. This leads to a gradual shift in the population's characteristics as the 'fittest' traits become more common.

environmental pressure

Environmental pressure refers to any external factor that influences an organism's survival and reproduction. These pressures can be abiotic, such as temperature and water availability, or biotic, like competition and predation. In the given bird population, the drought is the environmental pressure. It has made small seeds rare and large seeds more common. Such pressures force the population to adapt. Birds with beaks suited for eating hard seeds will thrive, while those that can't adapt will decline in number. Environmental pressures are a critical component of natural selection because they directly affect which traits are advantageous and become prevalent over generations.